The present invention relates to improved processes for spinning fibers that contain polybenzoxazole or polybenzothiazole polymer.
Lyotropic liquid crystalline polybenzoxazole and polybenzothiazole are not thermoplastic. They are typically made into fibers by dry-jet, wet-spinning techniques, in which a dope that contains the polybenzazole polymer and an acid solvent is spun through a spinneret, drawn across an air gap, and coagulated by contact with a fluid that dilutes the solvent and is a non-solvent for the polymer.
It is economically desirable to spin fibers at the highest speed possible, because the spinning equipment is very expensive. It is also desirable to spin individual filaments with as small a diameter as possible (low denier), because fibers that contain a large number of low denier filaments usually have better and more consistent physical properties than fibers that contain a small number of high denier filaments.
Unfortunately, at high speeds and low deniers, the filaments frequently break. It is desirable to develop techniques that will allow spinning of low-denier fibers at high speeds without frequent breakage of the filaments.